Charged particle beam systems are employed in various fields, such as electron microscopy, lithography, particle acceleration, and others. As one example, electron microscopes are useful tools for observing the surface topography and composition of a sample. In an electron beam tool used for microscopy, electrons are directed to a sample and may interact with the sample in various ways. For example, when an electron beam impinges on a sample, secondary electrons, backscattered electrons, auger electrons, x-rays, visible light, etc. may be scattered from the sample and directed to a detector. Scattered particles may form one or more beams incident on the detector.
To increase throughput, a multi-beam imaging (MBI) system may split a primary electron beam into a plurality of beamlets for scanning multiple separate areas of a sample simultaneously. After impinging on the sample, a plurality of beamlets of scattered or secondary electrons may be directed onto a detector. Typically, a detector for use in an MBI system may be provided with a plurality of sensing elements, for example, in the form of a pixelated array. Due to the effects of aberration and dispersion, multiple beam spots may overlap on the detector surface, leading to crosstalk. Furthermore, the beam spots may drift and change the locations at which detector sensing elements are activated for sensing the beam spot. Additional optical elements may be required to track the multiple beam spots and correct the projection of the beamlets, contributing to complexity and adding difficulties to scaling up detector systems. Additionally, when a fine detector array comprising a large number of sensing elements is provided, a switching matrix should also be provided to connect individual sensing elements associated with the same beam spot, introducing further complexity.